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Topic: Clip+ DC offset (Read 4986 times)

Hi, I've been hearing little squeaks when I pause my Clip+ and occasionally when playing so I decided to measure the DC offset. While playing it appears to be about 5mV but when I pause it it settles on anything from 0 to 60mV offset. I booted the original firmware and it seems to be 0.1mV while playing then 0mV when paused. Is this a problem? I imagine it is especially when amplified you could have upwards of 600mV. I'm not sure if it's related but a pair of IEMs I used almost exclusively with rockbox on this Clip+ have one channel partially broken (way quieter then the otherside).

Hi, I've been hearing little squeaks when I pause my Clip+ and occasionally when playing so I decided to measure the DC offset. While playing it appears to be about 5mV but when I pause it it settles on anything from 0 to 60mV offset.

I'm just measuring between ground and each channel with my multimeter. I brought it up because from what I've read making headphone amps you want the DC offset to be less than 20mV otherwise you can damage your headphones. It seems strange that it happens with rockbox and not the OF. I'll double check it tonight to makes sure i haven't made any errors.

ah yes you're quite correct I'll tie each channel to ground with a 1k resistor and see what I measure.

edit: tried that, no change. would it be possible that rockbox stays at the current sample when paused rather going to zero?

edit 2: turns out I had OF volume turned down compared to Rockbox so I turned it up and it measured the same 5mV approx while playing but went to zero when paused. I am thinking it could be the above because it varies every time it is paused and once paused it goes up and down as I change the volume. The worst I measured was 240mV with rockbox turned up to max.

I hear what must be the same thing on my Fuze v2 when pausing. It's not present, however, when Fade on Stop/Pause is disabled. It happens what seems like a second or two after the music stops. Could be right at the end of the fade out. Also happens at the start of resuming playback of a paused track.

Rockbox 3.7.1 and the IEMs being used are MEElectronics M11+, if that's relevant.

Righto I found I had r27228 on my computer so I installed that and it made no difference. But what I did find was that there is no squeak in silent parts of the music and none at all on a track of silence I have, so I do think the squeak is related to the offset as it was similar. Also I think there may be a squeak without fade to pause on as well but you just can't hear it over the music.

I just noticed on my Fuze that when it's paused adjusting the volume level results in a distinct clicking sound that can be heard at each volume increment at the upper levels. (Keyclicks are Off in the settings.) Could the cause for this noise be the same thing?